Fix undefined Rails version for other repos sub-builds

[pirj]

https://github.com/rspec/rspec-support/runs/4956870915?check_suite_focus=true

[JonRowe]

Maybe just do version = ... at the top and run the case statement of a local variable?

[pirj]

We skip this for:

• pre 6.1 because it doesn't have Action Mailbox
• 7.0.1+ because it does the same (presumably) itself

The only -stable build left is 5-2-stable that we'll drop.

In any case, this doesn't hurt on 3.1. And there's no other way to work around this for 6.1.

I don't really want to overcomplicate this.

Ideally, we could:

- version = ENV['RAILS_VERSION'] || (File.exist?(version_file) && File.read(version_file).chomp) || ''
+ version = ENV['RAILS_VERSION'] || (File.exist?(version_file) && File.read(version_file).chomp) || "~> 6.0.0"

and combine the last two branches.

This would allow to keep && version.split(' ').last < '7.0'.
Is it worth it?

[JonRowe]

Or we could return from the case statement a skip variable? Seems like skipping it on rails 7 is a good idea to ensure we don't change its behaviour?

[pirj]

I've just realized that it's not only for Rails 6.1.
On Rails 6.0 that is used in sub-builds, Action Mailer loads the mail gem, and it:

require 'net/smtp'

Adjusting accordingly.